diff --git a/lib/grape.rb b/lib/grape.rb
index 680bea819f..f4ec5701fa 100644
--- a/lib/grape.rb
+++ b/lib/grape.rb
@@ -42,6 +42,10 @@ def self.deprecator
     @deprecator ||= ActiveSupport::Deprecation.new('2.0', 'Grape')
   end
 
+  def self.rack3?
+    Gem::Version.new(::Rack.release) >= Gem::Version.new('3')
+  end
+
   eager_autoload do
     autoload :API
     autoload :Endpoint
diff --git a/lib/grape/http/headers.rb b/lib/grape/http/headers.rb
index 3014ccff0d..e8a368b82c 100644
--- a/lib/grape/http/headers.rb
+++ b/lib/grape/http/headers.rb
@@ -11,15 +11,7 @@ module Headers
       REQUEST_METHOD  = 'REQUEST_METHOD'
       QUERY_STRING    = 'QUERY_STRING'
 
-      if Gem::Version.new(Rack.release) < Gem::Version.new('3')
-        ALLOW             = 'Allow'
-        CACHE_CONTROL     = 'Cache-Control'
-        CONTENT_LENGTH    = 'Content-Length'
-        CONTENT_TYPE      = 'Content-Type'
-        LOCATION          = 'Location'
-        TRANSFER_ENCODING = 'Transfer-Encoding'
-        X_CASCADE         = 'X-Cascade'
-      else
+      if Grape.rack3?
         ALLOW             = 'allow'
         CACHE_CONTROL     = 'cache-control'
         CONTENT_LENGTH    = 'content-length'
@@ -27,6 +19,14 @@ module Headers
         LOCATION          = 'location'
         TRANSFER_ENCODING = 'transfer-encoding'
         X_CASCADE         = 'x-cascade'
+      else
+        ALLOW = 'Allow'
+        CACHE_CONTROL     = 'Cache-Control'
+        CONTENT_LENGTH    = 'Content-Length'
+        CONTENT_TYPE      = 'Content-Type'
+        LOCATION          = 'Location'
+        TRANSFER_ENCODING = 'Transfer-Encoding'
+        X_CASCADE         = 'X-Cascade'
       end
 
       GET     = 'GET'
diff --git a/lib/grape/request.rb b/lib/grape/request.rb
index 669f04f413..f522ea923b 100644
--- a/lib/grape/request.rb
+++ b/lib/grape/request.rb
@@ -46,12 +46,14 @@ def build_headers
       end
     end
 
-    def transform_header(header)
-      if Gem::Version.new(Rack.release) < Gem::Version.new('3')
-        -header[5..].split('_').map(&:capitalize).join('-')
-      else
+    if Grape.rack3?
+      def transform_header(header)
         -header[5..].tr('_', '-').downcase
       end
+    else
+      def transform_header(header)
+        -header[5..].split('_').map(&:capitalize).join('-')
+      end
     end
   end
 end
diff --git a/spec/support/headers_helpers.rb b/spec/support/headers_helpers.rb
index 05a8e133ac..c1389cf706 100644
--- a/spec/support/headers_helpers.rb
+++ b/spec/support/headers_helpers.rb
@@ -4,21 +4,7 @@ module Spec
   module Support
     module Helpers
       def rack_versioned_headers
-        if Gem::Version.new(Rack.release) < Gem::Version.new('3')
-          {
-            cache_control: 'Cache-Control',
-            content_length: 'Content-Length',
-            content_type: 'Content-Type',
-            grape_likes_symbolic: 'Grape-Likes-Symbolic',
-            location: 'Location',
-            symbol_header: 'Symbol-Header',
-            transfer_encoding: 'Transfer-Encoding',
-            x_access_token: 'X-Access-Token',
-            x_cascade: 'X-Cascade',
-            x_grape_client: 'X-Grape-Client',
-            x_grape_is_cool: 'X-Grape-Is-Cool'
-          }
-        else
+        if Grape.rack3?
           {
             cache_control: 'cache-control',
             content_length: 'content-length',
@@ -32,6 +18,21 @@ def rack_versioned_headers
             x_grape_client: 'x-grape-client',
             x_grape_is_cool: 'x-grape-is-cool'
           }
+        else
+          {
+            cache_control: 'Cache-Control',
+            content_length: 'Content-Length',
+            content_type: 'Content-Type',
+            grape_likes_symbolic: 'Grape-Likes-Symbolic',
+            location: 'Location',
+            symbol_header: 'Symbol-Header',
+            transfer_encoding: 'Transfer-Encoding',
+            x_access_token: 'X-Access-Token',
+            x_cascade: 'X-Cascade',
+            x_grape_client: 'X-Grape-Client',
+            x_grape_is_cool: 'X-Grape-Is-Cool'
+          }
+
         end
       end
     end